1. Field of the Invention
The present invention relates to a camera having a function to correct vibration, and more particularly to a camera having a vibration correcting function as provided with a photographing-mode selecting unit to enable selection of a successive photographing mode.
2. Related Background Art
For conventional cameras provided with a vibration correcting unit, there are a variety of suggestions of vibration correcting apparatus having the structure to enable image vibration correction, in which, in order to correct image vibration caused by a shake of camera or particularly by inclination of a camera, an angular velocity sensor is used as vibration detecting means for detecting the shake or vibration of camera so as to detect vibration conditions by obtaining an angular velocity of the vibration of camera thereby and then vibration correcting means is driven according to a result of the detection to shift a photographing lens system as a main optical system or a vibration correction optical system as a part of the photographing lens system in directions perpendicular to the optical axis.
In the cameras provided with such a vibration correcting mechanism, image vibration is suppressed by controlling movement of the photographing lens system or the part thereof as a vibration correction optical system, whereby picture photography can be performed without image vibration even in exposure at slower shutter speed than in normal photography.
In the conventional technology as described above, a vibration detecting circuit is arranged to stop after completion of photography of a frame in normal photography. The vibration detecting circuit, however, takes a considerable time before stabilization of the circuit at restart (recharge of power), once it stops (or once the power supply is cut). Therefore, stop and start of the vibration detecting circuit is repeated every photographing in the successive photographing mode, so that photographing intervals each need to be set to a sufficiently long time period. This resulted in a problem of losing a quick photographing property.
Further, the cameras having such a vibration correcting function perform sampling of vibration signals to calculate an absolute amount of vibration from a sensor output from the vibration detecting sensor, that is, a reference level of detected signals corresponding to a state in which the angular velocity is "0" (a state without vibration).
Namely, the angular velocity sensor as a vibration detecting sensor has unstable sensor outputs at angular velocity of "0" because of drift etc., which could cause a possibility of degradation of vibration correction accuracy. It is thus considered that an average value of sensor outputs is obtained within a predetermined time period and then sensor outputs are calibrated using the average value as an output without vibration. For this purpose, sampling of vibration signals and averaging thereof are carried out.
Here, some hundred ms to about one second is normally necessary for sampling operations to obtain satisfactory accuracy. Such sampling operations are carried out between actuation of a half-depression switch in a shutter release button and actuation of a full-depression switch in the shutter release button.
Meantime, the cameras having the vibration correcting function as described above have the following problems when the successive photographing mode is selected as a photographing mode to execute continuous photography while keeping the shutter release button depressed.
In the conventional cameras, the sampling operations of vibration signals for the second or successive frame in the continuous photography are carried out between an end of a one-frame winding operation of film and a start of the next exposure. This lengthens a time lag at release of the shutter release button, which resulted in a problem of losing a shutter chance.
When the cameras having the vibration correcting function as described above are subjected to continuous photographing by a photographing operation of camera, for example actuation of the half-depression and full-depression switches in the shutter release button, or by a photographing mode, for example the continuous photographing mode, the vibration detection accuracy, in turn the vibration correction accuracy, is influenced by timings when the vibration detecting unit or the vibration correcting unit is started or stopped. Therefore, it is required to take some measures to solve the above-described problems, taking the above points into consideration.